To increase the immunogenicity of the T241 fibrosarcoma, we are altering the host by either a) transplantation in an allogenic strain or b) prior prophylactic treatment of the syngeneic strain with gluteraldehyde treated tumor cells. The effects of these host alterations on the metastatic process will be studied. Also, we shall experimentally characterize BCG therapy on the metastatic process of a strongly immunogenic fibrosarcoma. Such a strongly immunogenic fibrosarcoma will be created by host alteration as described above and by a known, highly immunogenic fibrosarcoma. Furthermore, we plan to test the generality of our findings by studying a transplantable carcinoma. With the use of mathematical modeling, we shall a) develop parameter values which characterize the different tumor host systems before and after BCG therapy and b) formulate quantitative predictions for optimal scheduling immunotherapy.